Plunger for extrusion press

ABSTRACT

Disclosed is an elongated plunger body having an axial throughbore; a pressure head arranged for radial movement on the front face of the plunger body; a stem secured to the pressure head and passing with a clearance through the through-bore; the stem being formed at a central region thereof with a collar tightly fitting in the through-bore, and at the other end thereof being secured to the plunger body and locked against axial movement, whereby the flexibility of the stem portion between the pressure head and the collar allows elastic centering of the pressure head during the stroke of the plunger.

U l United States- Patent 1 [In 3,742,752 Maier July 3, 1973 PLUNGER FOREXTRUSION PRESS 1.032.206 6/1958 Germany 72/273 [75] Inventor: BrunoMaier, Worblingen, Germany h w Primary Examiner-C arles Lanham [73]Assignee. swlsihalulfnlfilltgm, Ltdl., lgeuhausen Asst-slam Examinerkoben M Rogers am me a wltzer an Attorney-Ernest F. Marmorek [22] Filed:Aug. 10, 1971 [21] App]. No; 170,546 57 ABSTRACT Disclosed is anelongated plunger body having an axial I [30] Foreign ApplicauonPriority Data through-bore; a pressure head arranged for radial Aug. 14,Switzerland movement on the front facc of plunger a tem secured to thepressure head and passing with a clear- U-S- Cl anc through the throughb re; the stem being formed [5 l Cl. at a central region thereof acollar in I [58] Field of Search 72/273, 478 the h hb and at the otherend th f being 1 secured to the plunger body and locked against axialReferences Clted movement, whereby the flexibility of the stem portionUNITED STATES PATENTS between the pressure head and the collar allowselastic 3,385,091 5/1968 Hess 72 273 centering offihe Pressure a duringthe Stroke of the FOREIGN PATENTS R APPLICATIONS plunge" 1,043,3559/1966 Great Britain 72/273 5 Claims, 2 Drawing Figures PATENTEDJUL aim37421752 SHEEI '1 BF 2 Fig.1

PLUNGER FOR EXTRUSION PRESS BACKGROUND OF THE INVENTION This inventionrelates, generally, to extrusion presses and, more specifically, to anarrangement of pressure heads on plungers of presses for extrusionshapes from light metals.

lt is known in presses for extrusion of metals how to arrange a pressurehead or a dummy head between the front end of a plunger body and'thematerial to be extruded against a press mandrel. In most cases, the pressure head has been loosely coupled with the front end surface of theplunger body, namely, without any positive connection. Such a prior artarrangement, however, has the disadvantage that after the completion ofthe extrusion process the detachable pressure head remains arrested onthe remnant of the billet and must be forcibly pushed out from thecontainer. Subsequently, the extrusion remnants are removed from thepressure heads either by means of a cup-shaped pressing tool within thepress, or manually outside the press, so that the same pressure head canbe re-employed in another extruding operation. The removal of extrusionremnants from the pressure head, however, is a timeconsuming processduring which the pressure head may become damaged.

In another known arrangement, the pressure head is positively coupledwith. the front surface of the plunger body; for example, by screwingthe pressure heads on a threaded end of the plunger. This measure has,in any event, the advantage that the pressure head does not remain inthe container during the return of the plunger 'after thecompletion ofthe extrusion process and that the aforementioned additional work isavoided. Nevertheless, the pressure heads which are rigidly tightened atthe end of the plunger body very quickly wear off and must be replacedafter a few days of operation.

The cause of this phenomenon occurring in a plunger with a rigidlyconnected head is in the. fact that the plunger and the container arenever accurately centered with respect one to the other; namely thelongitudinal axes of the plunger and of the container whichtheoretically should be mutually aligned are never truly lined up in anactual embodiment. The mutual deviation of the two longitudinal axes canbe proportional to the size of the extrusion press, namely, to thedistance which the front surface of the plunger has to travel withoutsupport towards the edge of the inlet opening of the container.

As a result, the pressure head which is firmly tightened to the plunger,strikes with a lateral deviationagainst the inlet opening of thecontainer and frequently it impacts against the edge of the containeropening and becomes damaged. In any event, during farther progress ofpenetration into the container, the pressure head is forced against oneside of the wall of the container with a greater force than against theopposite side. The resulting increased friction at one side of thecontainer wears off the pressure head and makes it, in a short time,unusable. 7

In another known'arrangement ofthe pressure head as described, forinstance, in the U.S. Pat. No. 3,385,091 to Relza .l. Hess, the pressurehead is supported on an elongated stem passing through an axial bore inthe plunger body. The stem has at its front region a guide portion ofenlarged diameter that fits the axial bore with a clearance. Similarly,a clearance is of the stem is secured to a nut which is axially movablewithin a recess at the rear end of the plunger body.

This arrangement allows some float of the pressure head; nevertheless,to keep the axial and radial play of the pressure head withinpredetermined limits, a very accurate dimensioning and machining of theentire structure is necessary. Consequently, the manufacture andreplacement of the dummy pressure head is very costly.

It is, therefore, an object of this invention to removethe disadvantagesof prior art arrangements of a pressure head in the extrusion press.

More specifically, an object of this invention is to provide a pressurehead which, within certain limits, will allow the centering of thepressure head within the extrusion container.

Another object of this invention is to provide a pressure head which isfirmly connected to the plunger body.

Still another object of this invention is to provide a pressure headwhich is wear-resistant, simple in manufacture and in its assembly, andwhich has a considerable lifetime.

SUMMARY OF THE INVENTION The above objects of this invention areattained 'by providing the pressure head with'a supporting elongatedstem which passes with a clearance through an axial bore in the plungerbo'dy whereby the center region of the stem is provided with a collarwhich tightly tits into the bore; the rear end of the stern is tightenedby a threaded nut against the rear end of the plunger body. Inthismanner, it is' achieved that, in spite of the fact that the stemislocked against axial movement, the relatively longportion of the stembetween the'pressur'e head and the collar allows, due to flexibility ofmaterial of the stem, a radial movement of the pressure head within thelimits ofthe clearance between the stem and the axial bore. Thetightening nut need notfit accurately into the recess at the rear faceof the plunger body and the stem within the bore is self-centering.

BRIEF DESCRIPTION OF THE DRAWING DETAILED DESCRIPTION Referring now toFIG. 1, the extrusion press l -includes an axially movable plunger 2with a pressure head 3 on its front'face. Under the-pressure of' theplunger 2, a metal material which has beeninserted into the inletopening 4- of a container 5 is extruded through an outlet opening 6having the form of a pressure die (not illustrated) and is shaped thusinto a de= sired form.

The plunger 2 comprises atubular plunger body hav# ing in its interior alongitudinal axial through bore 9'extending from a front face 7 to arear'face 8 of the 3 plunger body. The diameter of the plunger body issteplike extended towards the rear end of the latter and is providedwith a recess communicating with the through-bore 9.

The lower surface of the pressure head 3 mates with the front face 7 ofthe plunger body and is arranged for an axial movement thereon. The topsurface 11 of the pressure head facing the inlet opening of thecontainer 5 is symmetrically encased in its outer diameter with respectto the lower surface 12.

The center area of the lower surface 12 of the pressure head is rigidlyconnected with an elongated stem 13 passingwith a clearance through theaxial bore 9 in the plunger body. The opposite end of the stem 13 issecured to the rear face of the plunger body preferably by a screwconnection.

The diameter of the stem 13 is considerably smaller than the innerdiameter of the through-bore 9; the resulting clearance amounts toapproximately 40 percent of the diameter of the stem 13, for example. Toprevent movement in axial direction of the stem 13, a nut 14 is inengagement with a threaded end of the stem 13 projecting into the recess10.

According to the invention, a central region of the stem 13 is providedwith a collar-shaped portion 15 tightly fitting into the bore 9. It ispossible to provide the front portion of the stem between the collar 15and the nut 14 with additional tightly-fitting collars to reinforce thefixing effect of the central collar 15.

The front portion of the stem 13 between the collar 15 and the pressurehead 3, however, must be devoid of any collars, since this front;portionmust be capable of a flexible displacement in any radial directionwithin the limits of its clearance. Similarly, the pressure head 3 whichis arranged for radial movement on the front face 7 of the plunger body,yields, due to its elasticity, to such a small radial displacement ofthe front portion of the stem 13.

The arrangement of this invention makes it possible that the pressurehead is fixedly connected with the plunger body in the sense that duringthe traction of the plunger 2 after the completion of an extrusion cyclethe pressure head is withdrawn from the container 5 together with theplunger 2. On the other hand, the pressure head 3 is slidably seated onthe front face 7 of the plunger body so that the head 3 can accommodateitself during the penetration of the plunger into the recipient 5 toradial deviations in the alignment of axes of the plunger and of therecipient, thereby avoiding excessive one-sided loads actingtransversely to the longitudinal axis of the plunger. As a result,bending stresses caused by such one-sided loads are neutralized by thesupporting stem itself and not by the body of the plunger as the case isin prior art arrangement with rigidly mounted pressure heads. Theplunger, therefore, cannot be deformed.

The experience with extrusion presses equipped with the above-describedplunger arrangement according to this invention has shown that the pressis able to operate faultlessly for a long period of time without thereplacement of the pressure head, whereas the plungers of anotherstructure have to be replaced after several days of action. In addition,the arrangement of this invention eliminates the removal of pressbillets from the pressure head and consequently saves personal andoperational costs.

Variations and modifications may be made within the scope of theinvention. For example, it is also possible to make the bore 9 from thepressure head lower surface 7 so as to terminate about halfway in theplunger body; at the bottom of the bore 9 an inner thread can beprovided and a corresponding threaded end portion of the supporting stem13 is screwed in. The stem 13 in this case corresponds to the frontstern portion as described in the example of the previous embodiment andthe collar 15 is omitted. I

It will be understood that various materials and other structuraldetails may be employed within the scope of the appended claims.

I claim:

1. A plunger for an extrusion press, especially for extrusion of shapesof light metals comprising in combination an elongated plunger bodyhaving an axial bore, a

front face, and a rear face,

a pressure head arranged for radial movement relative to the front face,

an elongated stem secured at one end thereof near saidfront face to saidpressure head-and passing with a clearance through said bore, and

a collar for securing said stem in said bore, said collar arranged on acentral portion of said stem and tightly fitting in said bore, said stembeing disconnectably secured to said body near said rear face wherebythe flexibility of the stem portion between said collar and saidpressure head allows for radial displacement and central alignment ofsaid pressure head in a recipient.

2.- A plunger according to claim 1 wherein said clearance of said sternamounts to at least 40 percent of the diameter of said bore.

3. A plunger according to claim 1 wherein said stem is locked againstmovement in axial'direction.

4. A plunger according to claim 3 wherein said rear face includes arecessed portion, said other end of said stem being threaded and securedto said rear face by a nut located in said recessed portion.

5. A plunger according to claim 4 further comprising an additionaltightly fitting collar disposed between said central collar and saidnut.

s t s 4 s

1. A plunger for an extrusion press, especially for extrusion of shapesof light metals comprising in combination an elongated plunger bodyhaving an axial bore, a front face, and a rear face, a pressure headarranged for radial movement relative to the front face, an elongatedstem secured at one end thereof near said front face to said pressurehead and passing with a clearance througH said bore, and a collar forsecuring said stem in said bore, said collar arranged on a centralportion of said stem and tightly fitting in said bore, said stem beingdisconnectably secured to said body near said rear face whereby theflexibility of the stem portion between said collar and said pressurehead allows for radial displacement and central alignment of saidpressure head in a recipient.
 2. A plunger according to claim 1 whereinsaid clearance of said stem amounts to at least 40 percent of thediameter of said bore.
 3. A plunger according to claim 1 wherein saidstem is locked against movement in axial direction.
 4. A plungeraccording to claim 3 wherein said rear face includes a recessed portion,said other end of said stem being threaded and secured to said rear faceby a nut located in said recessed portion.
 5. A plunger according toclaim 4 further comprising an additional tightly fitting collar disposedbetween said central collar and said nut.